Anti Static Mats
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Due to the recent subject of Anti Static mats, I did a little googling
and thought I'd share my findings. First for reference Alan Bloom had this to say back in Feb 27, 2008 http://elecraft.365791.n2.nabble.com/Radio-Shack-ESD-mat-doesn-t-meet-spec-td462383.html <quote> Here are the results: Radio Shack P/N 276-2370 ($22.99) - 26 G ohms (26,000 M ohms) Jameco P/N 10584 ($16.45) - 44 G ohms (44,000 M ohms) Digi-Key P/N 16-1121-ND, (Desco 66164) ($38.18) - 41 M ohms The Desco mat's resistance is about 1000x lower than the cheaper ones! This mat is quite large, (2 x 3 feet, 61 x 91.4 cm) so if you buy one you may need to cut it down to fit on your workbench. It comes with a "common point ground kit" (that you have to install on the mat yourself) that provides a long wire with solder lug to connect to ground and a two-socket connector for connecting one or two wrist straps. The wrist strap and cord have to be purchased separately. It looks like Digi-Key P/N SCP172-ND for $8.95 should work. So the total cost is about $47. But the cheap mats are no bargain if they don't work. </quote> Alan mentioned the Desco 66164 mat. DigiKey still sells them, but they are no longer $45, they are now $89 Google came up with different sellers priced from $60 to $96 https://www.google.com/search?q=Desco+66164&tbm=shop I did run across a similar product by Sierra for $43 the spec for the Desco and Sierra are stated as follows: (there are detailed .pdf's on the Technical Information tabs at the following links) Desco 66164 Property Test Method Value RTG Resistance: ANSI/ESD S4.1 10E6-10E8 ohms RTT Resistance: ANSI/ESD S4.1 10E6-10E8 ohms RTT Resistance: ANSI/ESD S4.1 <10E6 ohms Our Price: $60.14 Regular Price: $76.88 Our Part #: 66164 MFG's Part #: 66164 Estimated Weight: 3.4 lbs. http://www.all-spec.com/products/66164.html === === Sierra FS Series - 2-Layer Dissipative/Conductive Rubber Matting, .080" Thick Property Test Method Value RTG Resistance: 1 x 10E7 to 9 x 10E8 ohms RTT (Point to Point) 1 x 10E6 to 9 x 10E8 ohms Our Price: $43.15 Regular Price: $49.61 Our Part #: FSW100B MFG's Part #: FSW100B Estimated Weight: 4 lbs. http://www.all-spec.com/products/FSW100B.html maybe Alan or someone more knowledgeable than I can let us know if the Sierra is really up to the standards we need met? not part of any of the above companies, just relating what I found surfing on the subject -- GB & 73 K5OAI Sam Morgan ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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One thing worth noting: 1000x lower resistance isn't necessarily better,
especially given that it's not uncommon to have a battery in modern gear. The mat isn't supposed to ground everything, it's supposed to bleed off static charges. It's also why wrist straps or something to ground you are good, but should have several mega ohms of resistance -- you don't want to touch something that has some voltage on it and complete a low-impedance circuit to ground. Just FWIW. 73 -- Lynn On 4/6/2014 1:10 PM, Sam Morgan wrote: > Here are the results: > > Radio Shack P/N 276-2370 ($22.99) - 26 G ohms (26,000 M ohms) > Jameco P/N 10584 ($16.45) - 44 G ohms (44,000 M ohms) > Digi-Key P/N 16-1121-ND, (Desco 66164) ($38.18) - 41 M ohms > > The Desco mat's resistance is about 1000x lower than the cheaper ones! ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by k5oai
On 04/06/2014 01:10 PM, Sam Morgan wrote:
> Due to the recent subject of Anti Static mats, I did a little googling > and thought I'd share my findings. ... > maybe Alan or someone more knowledgeable than I can let us know if the > Sierra is really up to the standards we need met? From my 2010 posting http://www.mail-archive.com/elecraft%40mailman.qth.net/msg94407.html "So my recommendation is to buy a mat such as the Desco model that has a data sheet that specifies that it meets ANSI/ESD S4.1 or ANSI/ESD S20.20." I recommend against using a mat that has no specifications other than asserting it is an "anti-static mat." I found that the two I bought and tested both had too high a resistance to do any good. ======================= On 04/06/2014 02:20 PM, Lynn W. Taylor, WB6UUT wrote: > One thing worth noting: 1000x lower resistance isn't necessarily > better, Right, you don't want the mat to be too low a resistance either. Do not substitute a metal sheet for an anti-static mat. That just makes it even more likely you will zap something. ======================= On 04/06/2014 01:43 PM, Larry Lopez wrote: > They made me take an ESD course at work and well I have a few > comments I feel forced to make. Larry had a number of good points, for example: > When you have a discharge you might have failures months or years > later. It may be damaged and it may work fine. > > For a while. Exactly right. ESD is insidious. People think that if you didn't feel a "zap" when you touch something that there was no electro-static discharge. But a discharge that you can't feel can still be enough to damage a sensitive part. ======================= On 04/06/2014 12:10 PM, Fred Townsend wrote: ... > As a consultant I have done ESD audits of factories. If they know > the audit is coming all the wrist straps are in place. Surprise > audits are another thing. I find the straps and footwear to be > rarely used. How can they get away with that? The answer is they > have good work habits that avoid ESD problems rather than bleeding > off static build up. I think in many cases they actually are not getting away with it as well as they think. Part failures happen for a reason. If the reason can't be found it could well have been ESD. Some factories do in fact strictly enforce static-safe procedures. HP/Agilent "got religion" on this many years ago, at least here in Sonoma County CA. > Here are a few everyday hints the pros use. > 1. Wear cotton! ... [etc. etc.] All those suggestions can help, but they are not foolproof. It requires constant vigilance to make sure you don't make a mistake. Rather than go to all that trouble, why not just use the anti-static mat and wrist strap and be done with it? If the wrist strap is too awkward, an ankle strap is a good alternative. Alan N1AL ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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oops never mind, I just reread the pdf on the Sierra FS and it's made in
China, where as the Desco is made in the US (or so they say) On 4/6/2014 9:00 PM, Alan Bloom wrote: > I recommend against using a mat that has no specifications other than > asserting it is an "anti-static mat." I found that the two I bought and > tested both had too high a resistance to do any good. -- GB & 73 K5OAI Sam Morgan ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by k5oai
I was once asked if the mats on my assembly line were antistatic. I thought they were but I wasn’t sure since I didn’t buy them. The mats took a beating and only lasted a year or two. Some were new and some were in tatters. I flipped over a new mat. It clearly said antistatic but the older mats didn’t have any labels and they looked different. I took an ohmmeter, stabbing the probes in about an inch apart. No reading. No reading for the new mats or the antistatic bags we used by the thousands. After rubbing with fur, a triboelectric meter (a meter used for measuring static charge) was used on the mats and bags without measuring a charge. My conclusion was surfaces could be antistatic without measuring any resistance. Same for bags. If you have one from your Elecraft kit, try measuring it with an ohmmeter. 73 Fred, AE6QL -----Original Message----- >From: Sam Morgan <[hidden email]> >Sent: Apr 6, 2014 7:21 PM >To: [hidden email] >Subject: Re: [Elecraft] Anti Static Mats > >oops never mind, I just reread the pdf on the Sierra FS and it's made in >China, where as the Desco is made in the US (or so they say) > >On 4/6/2014 9:00 PM, Alan Bloom wrote: > >> I recommend against using a mat that has no specifications other than >> asserting it is an "anti-static mat." I found that the two I bought and >> tested both had too high a resistance to do any good. > >-- >GB & 73 >K5OAI >Sam Morgan ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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On 04/06/2014 09:24 PM, Fred Townsend wrote:
> ...I flipped over a new mat. It clearly said antistatic but the > older mats didn’t have any labels and they looked different. > I took an ohmmeter, stabbing the probes in about an inch apart. > No reading. You can't measure the mat resistance with an ohm meter. Or to be more accurate, if you get a reading on the meter, then the resistance is way too low. The resistance between a pair of meter probes would typically be in the range of 100's of megohms or more, which is too high to measure with a multimeter. At the bottom of this message is a description of the test procedure I used: http://www.mail-archive.com/elecraft%40mailman.qth.net/msg94407.html Alan N1AL ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by k5oai
Alan if you call the fire department about a cat up a tree they will ask if you have ever seen a dead cat in a tree inferring that the cat will find its own way down from the tree without help. If the resistance and maintenance of the mat are so critical don't you think we would reports of dead mats by now? 73 Fred, AE6QL -----Original Message----- >From: Fred Townsend <[hidden email]> >Sent: Apr 6, 2014 9:24 PM >To: Sam Morgan <[hidden email]>, [hidden email] >Subject: Re: [Elecraft] Anti Static Mats > > >I was once asked if the mats on my assembly line were antistatic. I thought they were but I wasn’t sure since I didn’t buy them. The mats took a beating and only lasted a year or two. Some were new and some were in tatters. I flipped over a new mat. It clearly said antistatic but the older mats didn’t have any labels and they looked different. I took an ohmmeter, stabbing the probes in about an inch apart. No reading. No reading for the new mats or the antistatic bags we used by the thousands. After rubbing with fur, a triboelectric meter (a meter used for measuring static charge) was used on the mats and bags without measuring a charge. > >My conclusion was surfaces could be antistatic without measuring any resistance. Same for bags. If you have one from your Elecraft kit, try measuring it with an ohmmeter. >73 >Fred, AE6QL > > >-----Original Message----- >>From: Sam Morgan <[hidden email]> >>Sent: Apr 6, 2014 7:21 PM >>To: [hidden email] >>Subject: Re: [Elecraft] Anti Static Mats >> >>oops never mind, I just reread the pdf on the Sierra FS and it's made in >>China, where as the Desco is made in the US (or so they say) >> >>On 4/6/2014 9:00 PM, Alan Bloom wrote: >> >>> I recommend against using a mat that has no specifications other than >>> asserting it is an "anti-static mat." I found that the two I bought and >>> tested both had too high a resistance to do any good. >> >>-- >>GB & 73 >>K5OAI >>Sam Morgan > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Alan Bloom
if you put a sensitive part
on a something that conducts well then you get a static discharge and damage. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Fred Townsend-2
If I got such an answer from a fire department, I would tell them that
the dead cat may well be hidden in the tree, and once dead would likely attract nature's sanitation team and they would likely remove the dead cat with at least as much efficiency as the fire department can muster. If the cat is injured, it may need help that it can not provide for it's self. I'm not a cat lover, I just don't think this analogy is worth much. (And, not trying to start a budget discussion--I would not call the fire department, but a five-year old kid might). A bad anti-static mat may relate more to the sick cat than the dead cat. When you pull on the tail of the sick cat you may get a weak mew that may eventually go silent, returning this thread back to radio through reference to an old wireless metaphor. YMMD Richard Hill On 4/6/2014 10:16 PM, Fred Townsend wrote: > Alan if you call the fire department about a cat up a tree they will ask if you have ever seen a dead cat in a tree inferring that the cat will find its own way down from the tree without help. > > If the resistance and maintenance of the mat are so critical don't you think we would reports of dead mats by now? > 73 > Fred, AE6QL > > > > -----Original Message----- >> From: Fred Townsend <[hidden email]> >> Sent: Apr 6, 2014 9:24 PM >> To: Sam Morgan <[hidden email]>, [hidden email] >> Subject: Re: [Elecraft] Anti Static Mats >> >> >> I was once asked if the mats on my assembly line were antistatic. I thought they were but I wasn’t sure since I didn’t buy them. The mats took a beating and only lasted a year or two. Some were new and some were in tatters. I flipped over a new mat. It clearly said antistatic but the older mats didn’t have any labels and they looked different. I took an ohmmeter, stabbing the probes in about an inch apart. No reading. No reading for the new mats or the antistatic bags we used by the thousands. After rubbing with fur, a triboelectric meter (a meter used for measuring static charge) was used on the mats and bags without measuring a charge. >> >> My conclusion was surfaces could be antistatic without measuring any resistance. Same for bags. If you have one from your Elecraft kit, try measuring it with an ohmmeter. >> 73 >> Fred, AE6QL >> >> >> -----Original Message----- >>> From: Sam Morgan <[hidden email]> >>> Sent: Apr 6, 2014 7:21 PM >>> To: [hidden email] >>> Subject: Re: [Elecraft] Anti Static Mats >>> >>> oops never mind, I just reread the pdf on the Sierra FS and it's made in >>> China, where as the Desco is made in the US (or so they say) >>> >>> On 4/6/2014 9:00 PM, Alan Bloom wrote: >>> >>>> I recommend against using a mat that has no specifications other than >>>> asserting it is an "anti-static mat." I found that the two I bought and >>>> tested both had too high a resistance to do any good. >>> -- >>> GB & 73 >>> K5OAI >>> Sam Morgan > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by k5oai
That would mean the part was charged. How would that happen?
-----Original Message----- >From: "Lawrence D. Lopez" <[hidden email]> >Sent: Apr 7, 2014 5:23 AM >To: Alan Bloom <[hidden email]> >Cc: [hidden email] >Subject: Re: [Elecraft] Anti Static Mats > >if you put a sensitive part >on a something that conducts >well then you get a static >discharge and damage. >______________________________________________________________ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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The human body can store quite a bit of charge. When you lay a part on
a conductive surface, charge flows between your body and the surface, through the part. That's why (if you don't have an anti-static mat and wrist strap) you should always touch the chassis, PC board, whatever with your other hand before placing a part on it. Alan N1AL On 04/07/2014 09:47 PM, Fred Townsend wrote: > That would mean the part was charged. How would that happen? > > > -----Original Message----- >> From: "Lawrence D. Lopez" <[hidden email]> >> Sent: Apr 7, 2014 5:23 AM >> To: Alan Bloom <[hidden email]> >> Cc: [hidden email] >> Subject: Re: [Elecraft] Anti Static Mats >> >> if you put a sensitive part >> on a something that conducts >> well then you get a static >> discharge and damage. >> ______________________________________________________________ > > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Fred Townsend-2
When one touches it, a charge is developed - then when it comes in
contact with a fully conducting surface, damage can occur. If instead you are working on a proper anti-static mat, the charge from your body and the part is dissipated slowly, no damage will be done and everything will be at the same potential. 73, Don W3FPR On 4/8/2014 12:47 AM, Fred Townsend wrote: > That would mean the part was charged. How would that happen? > > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by k5oai
Greetings, all.
Dave Jones, who runs the EEVblog, has a few videos relating to anti-static bags and mats. The first one that talks about anti-static bags is worth watching. It shows the difference between the common pink anti-static bags and the silvery static shielding bags. Those pink bags and the related "anti-static" chip carriers don't do as much to protect your components as you might think. http://www.eevblog.com/2012/02/25/eevblog-247-anti-static-bag-myth-revisted/ http://www.eevblog.com/2012/03/01/eevblog-250-anti-static-mat-myth/ http://www.eevblog.com/2014/03/02/eevblog-585-lab-bench-esd-matting-upgrade-tagarno-hd-microscope/ The first part of the third video (mainly starting around 2.5 minutes in) talks about ESD matting that Dave was putting down on his lab benches. -- Cheers! Kevin. http://www.ve3syb.ca/ |"Nerds make the shiny things that distract Owner of Elecraft K2 #2172 | the mouth-breathers, and that's why we're | powerful!" #include <disclaimer/favourite> | --Chris Hardwick ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Hard to figure out what he is trying to prove. Finally on the antistatic mat issue, his point was that it doesn't affect measurements made with circuits lying on the mat. I guess I was thinking that he would show us how the mat is antistatic, as he did with the bags.
<quote author="Kevin Cozens-2"> Greetings, all. Dave Jones, who runs the EEVblog, has a few videos relating to anti-static bags and mats. The first one that talks about anti-static bags is worth watching. It shows the difference between the common pink anti-static bags and the silvery static shielding bags. Those pink bags and the related "anti-static" chip carriers don't do as much to protect your components as you might think. http://www.eevblog.com/2012/02/25/eevblog-247-anti-static-bag-myth-revisted/ http://www.eevblog.com/2012/03/01/eevblog-250-anti-static-mat-myth/ http://www.eevblog.com/2014/03/02/eevblog-585-lab-bench-esd-matting-upgrade-tagarno-hd-microscope/ The first part of the third video (mainly starting around 2.5 minutes in) talks about ESD matting that Dave was putting down on his lab benches. -- Cheers! Kevin. http://www.ve3syb.ca/ |"Nerds make the shiny things that distract Owner of Elecraft K2 #2172 | the mouth-breathers, and that's why we're | powerful!" #include <disclaimer/favourite> | --Chris Hardwick
Chuck, KE9UW
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In reply to this post by Richard-3
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In reply to this post by k5oai
Don, if you mean by ‘developed’ a charge is generated then no, the triboelectric effect doesn’t work that way. See http://en.wikipedia.org/wiki/Triboelectric_effect.
If you mean the previously, developed by friction on the body, charge is transferred then yes, but then in only in a very limited way. A RC of 47 ohms and 1500 pf is often used to model the human body. The charge transferred will be in proportion to the surface capacity of the touched object. Small objects tend to have a very small surface capacity so little or no charge is transferred. Back to the subject at hand. What part do the antistatic mats play? The argument Alan seems to make is there is an optimal resistance for the anti-static mat and that is critical to maintain the mat within that range. To that I say the Emperor has no clothes. There are really two issues here. 1. How do I prevent static from being developed in the first place? 2. How is a developed charge going to hurt my component? With regard to mats, just about any soft rubber mat will not react to the triboelectric effect so it is passes item 1 above. Hard rubber, plastic or other dielectric materials such as Formica or Varathane tabletops are questionable. With regard to item 2) components are damaged when either their dielectric limits or their current carrying capacity are exceeded. By definition antistatic mats do not build up a charge so exceeding dielectric limits seems improvable and so that brings us down to exceeding current limits. The argument has been made that when a high voltage charge it is discharged through the mat that the discharge must not be too fast nor too slow. It must be just right. To Goldilocks and her followers I say no it’s not so. I think a proof here is beyond the scope of this forum. However, an examination of the human body model (47 ohms and 1500 pf) will easily lead to that proof. For those still not convinced I offer this except from the first TI data sheet I picked up. It states: “ESD Protection Exceeds JESD 22”. Yes there is a manufacture’s requirement for antistatic endurance. If they don’t exceed JESD22, then special packaging and markings are required. You’ll know to take extra special precautions when you see the labels. 73 Fred, AE6QL -----Original Message----- >From: Don Wilhelm <[hidden email]> >Sent: Apr 7, 2014 10:37 PM >To: [hidden email] >Subject: Re: [Elecraft] Anti Static Mats > >When one touches it, a charge is developed - then when it comes in >contact with a fully conducting surface, damage can occur. If instead >you are working on a proper anti-static mat, the charge from your body >and the part is dissipated slowly, no damage will be done and everything >will be at the same potential. > >73, >Don W3FPR > >On 4/8/2014 12:47 AM, Fred Townsend wrote: >> That would mean the part was charged. How would that happen? >> >> ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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On 04/13/2014 04:54 PM, Fred Townsend wrote:
> The argument has been made that when a high voltage charge it > is discharged through the mat that the discharge must not be > too fast nor too slow. It must be just right. To Goldilocks > and her followers I say no it’s not so. Not "just right" but within an acceptable range. > A RC of 47 ohms and 1500 pf is often used to model the human body. The human body model I am familiar with is 100 pf / 1500 ohms http://en.wikipedia.org/wiki/Human_body_model . If the human body is charged to 10kV, then when when you touch something grounded a current of 6.7A flows for 150 ns. That's too short a time to injure you but definitely enough to wake you up. If you are holding an electronic device and touch it to something grounded then that current will flow through the device. That's why you really don't want to use a metal plate in place of an anti-static mat. The mat has a high resistance in order to limit the current from an electro-static discharge. Even if the metal plate is not grounded directly it still has some capacitance to ground. Assuming, let's say, 10 pF then you still get 6.7A but it flows for only 15 ns. That's still more than enough to destroy a sensitive electronic device. So you don't want the mat resistance to be too low. If the mat resistance is too high, then it can't perform its other task of equalizing the voltage on all the devices placed on the mat (and the body of the operator, connected through the wrist strap). So yes, the mat resistance needs to be within a certain range. That is why industry standards have been created to specify that. Alan N1AL ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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